The hours you're barefoot are the ones that hurt
People spend a fortune on work shoes and then walk on a tile kitchen floor in bare feet for four hours a night. If your heel is worst on the first steps in the morning, or if it flares after an evening at home, that's not a coincidence.
Look at this one side on: there's a real arch shape in the footbed, the same idea Aetrex builds into their shoes, not the flat sheet of foam a normal slipper gives you. That's the whole reason to own a pair.